The present invention relates to methods and apparatus for inserting into the earth and extracting from the earth elongate members and, more particularly, to apparatus and methods for inserting wick drain material into the earth.
For certain construction projects, elongate members such as piles, anchor members, caissons, and mandrels for inserting wick drain material must be placed into and in some cases withdrawn from the earth. It is well-known that, in many cases, such rigid members may be driven into and withdrawn from the earth without prior excavation.
The present invention is particularly advantageous when employed to insert a mandrel carrying wick drain material into the earth, and that application will be described in detail herein. However, the present invention may have broader application to the insertion into and removal from the ground of other elongate members such as piles, anchor members, and caissons, especially when these members must be driven at an angle with respect to horizontal. Accordingly, the scope of the present invention should be determined by the scope of the claims appended hereto and not the following detailed description.
Because wick drain material is flexible, it cannot be directly driven into the earth. Instead, it is normally placed within a rigid mandrel that is driven into the earth. Once the mandrel and wick drain material have been driven into the earth, the mandrel alone is removed from the earth, leaving the wick drain material in place. The wick drain material that is left in place wicks moisture in its vicinity to the surface to stabilize the ground at that point.
Two basic systems are employed to drive mandrels into and remove mandrels from the earth. A first system is referred to as a top drive system and engages the upper end of the mandrel to insert the mandrel into the earth. In a top drive system, the upper end of the mandrel is securely attached to the drive system and forced downward or upward to insert the mandrel into or remove the mandrel from the ground. The upper end of the mandrel may also be vibrated by a vibratory drive means and/or crowded by a chain or cable drive means to cause the mandrel to penetrate the earth.
The primary disadvantage with the top drive system is that they require a substantial boom structure to support the mandrel and associated drive means. The requirement of a large and heavy boom structure limits the length of the mandrel that may be driven by a top drive system. Further, as the ground into which the wick drain material is to be inserted may be wet and unstable, the ground may not be sufficiently stable to support the required boom structure. Top drive systems thus may be inappropriate in certain situations.
A second system for inserting and removing mandrels engages the bottom end of the mandrel and will be referred to herein as a bottom drive system. A bottom drive system is not attached to any one point on the mandrel; instead, rotating roller surfaces and/or gear teeth engage the mandrel in a manner that displaces the mandrel along its axis to drive it into the ground.
Bottom drive systems require a boom sufficient to support only the mandrel; the boom for a bottom drive system may thus be significantly lighter than that for a top drive system, which alleviates some of the problems associated with large booms.
However, the primary disadvantage with known bottom drive systems is that they rely entirely on the roller or gear drive system for insertion and removal of the mandrel. Bottom drive systems do not have the benefit of a vibratory device for situations in which the mandrel becomes stuck due to soil conditions.
Accordingly, an important object of the present invention is to provide improved apparatus and methods for driving elongate members into and removing elongate members from the ground.
U.S. Pat. No. 5,213,449 to Morris shows, and USSR Patent No. SU 1027357 appears to show, bottom drive devices for driving a mandrel into the ground. The Morris patent discloses a gear dive system and the USSR patent appears to show a roller drive system.
Top drive wick drain inserters are disclosed in U.S. Pat. No. 3,891,186 to Thorsell, U.S. Pat. No. 4,166,508 to van den Berg, U.S. Pat. No. 4,755,080 to Cortlever et al., Dutch Pat. No. 65252, Dutch Pat. No. 7805153, and Dutch Pat. No. 7,707,303.
The Thorsell patent employs a chain attached to the top of a wick drain mandrel to crowd the mandrel into the ground.
The van den Berg patent employs a two-part mandrel, with the two parts being wound around rollers and crowded into the ground by unwinding the rollers.
The Cortlever et al. patent discloses a cable connected to the upper end of the mandrel and a hydraulic system for displacing the cable to drive or crowd the mandrel into the ground.
The Dutch ""252 and ""153 patents appear to employ a chain to drive or crowd a mandrel into the ground.
In the Dutch ""703 patent, a vibratory device appears to be fixed to the top end of the mandrel to drive the mandrel into the ground.
Shown in U.S. Pat. Nos. 5,117,544 and 5,117,925 issued to the Applicant are vibratory devices for driving piles into the earth. These patents disclose placing the vibratory device on top of the pile to be driven and vibrating the pile along its axis; the combination of the vibratory forces along the axis of the pile and the weight of the pile and vibratory device drives the pile into the ground. Caissons may be driven into the ground in the same manner.
The present invention is a drive system for inserting an elongate member into the ground. The drive system comprises a drive plate, a support system, an insertion housing, at least one drive gear, and a vibratory system for creating vibratory forces. The support system that engages the ground and supports the support plate at a substantially fixed height above a desired location. The suppression system is operatively connected between the support plate and the insertion housing to support the insertion housing above the desired location and resiliently oppose relative movement between the support plate and the insertion housing. The at least one drive gear is mounted to the insertion housing and engages the elongate member such that rotation of the drive gear displaces the elongate member along its longitudinal axis. The vibratory system is mounted to the insertion housing such that the vibratory forces are transmitted to the elongate member through the at least one drive gear. Rotation of the drive gear crowds the elongate member into the ground. Operation of the vibratory system vibrates the elongate member into the ground. Rotation of the drive gear and operation of the vibratory system together crowds and vibrates the elongate member into the ground.